Sergio Tucci

The Ligurian Sea: present status, problems and perspectives

The Ligurian Sea is a deep basin in the northernmost sector of the western Mediterranean which shows peculiar hydrodynamic and meteo-oceanographic features. The coasts of the Ligurian Sea are among the most urbanised and industrialised along the Italian coastline: the main causes of disturbance being littoral urban development and harbour activities, the building of littoral rail- and highways, and the presence of several polluted discharges. This review, by evaluating the huge scientific output published in the last three decades, describes and discusses the most important geological, hydrological and biological characteristics of the Ligurian Sea. We show that this regional sea has largely been investigated in terms of its geological and structural evolution, as well as in terms of the sedimentation dynamics of the littoral and deep bottoms, with particular attention to the sedimentation balance of the beaches and their erosive processes. We report that the prevalent hydrodynamic and meteo-oceanographic conditions favour a continuous exchange of coastal water masses, and that the seasonal and interannual dynamics of water masses can effects the local climate, with direct and indirect consequences on fish and benthic communities documented in the last decade. We stress that although recent studies offer good knowledge of the distribution of coastal benthic communities, only scant information is available for the whole continental shelf, the submarine canyons and the rocky bathyal bottoms. Our meta-analysis reveals that significant fishing activities are monitored, but also that certain sectors of the biological resource are suffering, and suggests the set up of appropriate management measures. The Ligurian Sea hosts a number of Marine Protected Areas (MPAs) of high relevance, while the institution of the Whale Sanctuary completes the protection policy of the Regione Liguria. Our meta-analysis points out the need for long-term studies, based primarily on the analysis of those areas of the Ligurian Sea that have been little investigated to date. Finally, only properly addressed studies, using experimental approaches and along appropriate spatial and temporal scales, might allow us to understand the functioning of the Ligurian marine ecosystems, evaluate their health conditions and the dynamics of the main variables that affect the distribution of the single species (including species of high economic value) and benthic communities.

Water Masses and Suspended Matter Characteristics of the Western Ross Sea

As part of an interdisciplinary field project performed during the austral summer 1994/95 devoted to examine the physical and bio-geochemical characteristics of the Ross Sea, hydrological stations were operated in the western sector off Victoria Land and water samples were collected at different depths of the water column to determine the particulate matter content. These investigations were carried out in the framework of the CLIMA (Climatic Long-Term Interaction for the Mass Balance in Antarctica) project of the Italian PNRA (National Program of Research in Antarctica).

Particulate matter and plankton dynamics in the Ross Sea Polynya of Terra Nova Bay during the Austral Summer 1997/98

Abstract The structure and variability of the plankton community and the distribution and composition of suspended particulate matter, were investigated in the polynya of Terra Nova Bay (western Ross Sea) during the austral summer 1997/1998, with the ultimate objective of understanding the trophic control of carbon export from the upper water column. Sampling was conducted along a transect parallel to the shore, near the retreating ice edge at the beginning of December, closer to the coast at the beginning of February, and more offshore in late February. Hydrological casts and water sampling were performed at several depths to measure total particulate matter (TPM), particulate organic carbon (POC), biogenic silica (BSi), chlorophyll a (Chl a ) and phaeopigment (Phaeo) concentrations. Subsamples were taken for counting autotrophic and heterotrophic pico- and nanoplankton and to assess the abundance and composition of microphyto- and microzooplankton. Statistical analysis identified two major groups of samples: the first included the most coastal surface samples of early December, characterized by the prevalence of autotrophic nanoplankton biomass; the second included all the remaining samples and was dominated by microphytoplankton. With regard to the relation of the plankton community composition to the biogenic suspended and sinking material, we identified the succession of three distinct periods. In early December Phaeocystis dominated the plankton assemblage in the well-mixed water column, while at the retreating ice-edge a bloom of small diatoms (ND) was developing in the lens of superficial diluted water. Concentrations of biogenic particulates were generally low and confined to the uppermost layer. The very low downward fluxes, the near absence of faecal pellets and the high Chl a /Phaeo ratios suggested that the herbivorous food web was not established yet or, at least, was not working efficiently. In early February the superficial pycnocline and the increased water column stability favoured the development of the most intense bloom of the season, essentially sustained by micro-sized diatoms (MD). The shift of the autotrophic community toward this size component produced major changes in the composition of particulate matter and determined its export to depth. The particulate organic carbon (POC)/chlorophyll a (Chl a ) and Chl a /Phaeo ratios more than halved, biogenic silica (BSi)/POC and BSi/Chl a strongly increased. Downward fluxes were greatly enhanced (reaching the yearly maximum) and essentially occurred via faecal pellets, underscoring the high efficiency of the herbivorous food web. In late February the deepening of the pycnocline, together with the decrease in light intensity, contributed to halting the diatom bloom. The biomass of small heterotrophs (HNF and MCZ) significantly increased relative to the previous period, favouring the shift toward a mistivorous food web (sensu [Ophelia 41 (1995) 153]) and resulting in the retention of biogenic matter in the superficial layer. Only in early February, with the increase in the size of primary producers (essentially represented by micro-sized diatoms), did the grazing food web become efficient [S. Afr. J. Mar. Sci. 12 (1992) 477], fuelling the long-lived carbon pool and enhancing export to depth (and hence carbon sequestration) via the sinking of large diatoms and high amounts of faecal pellets. The conditions predominating in the Terra Nova Bay polynya in mid-summer probably increased the efficiency of the CO 2 pump, possibly causing the Bay to act as a carbon sink.

Technical and public approaches to involve dredging stakeholders and citizens in the development of a port area

The stakeholders involved in a dredging operation are many and varied, some specifically involved in the technical aspects (client and dredging operators, organisations involved in legislative matters and/or environmental monitoring), and others less so (general public).These different kinds of stakeholders need different information and consequently different kind of data need to be produced (description of dredging objectives and scope, technical dredges characteristics, related legislation, environmental monitoring data, work progress, etc.) that need to be managed to share dredging information and knowledge. Here, we illustrate two examples of communication strategy adopted in the case of the dredging of the Port of Genoa (Italy) to ensure the correct data dissemination among the project partners and to the public. The first realized with a WebGIS (MArine Coastal Information SysTEm—Port Section, MACISTE-PS), a technology composed of data handling tools for storage, recovery, management and analysis of spatial data, and the second with a set of different communication products (posters, article publications, congress participations, website, etc.). The adoption of these two strategies assures us the dissemination of dredging information to a broad spectrum of people.

Physical and sedimentological characterisation of dredged sediments

Port dredging operations inevitably create a turbid plume around the dredge and it is necessary to follow the movement of this to impede its diffusion into the surrounding environment and reduce any negative impacts. To characterise the extension and concentration of the plume induced by dredging it is necessary to study the physical properties of the water, the residence time of the sediments in the water column and the diffusion velocity of the water and sediments. It is also essential to characterise the area and determine the specifics of the port environment under so-called normal maritime-traffic conditions. During the initial stage of such a study it is necessary to obtain measurements under diverse wind–wave conditions to characterise the physical features of the water column of the port area, the turbidity, the quantity and dimension of the suspended particulate matter and the current dynamics. In this article we present a series of physico-sedimentological operations to characterise a zone to be dredged based upon our experience during pre-dredging work in the Port of Genoa (Italy).

Simulations of dredged sediment spreading on a Posidonia oceanica meadow off the Ligurian coast, Northwestern Mediterranean

The sandy deposits from dredging can have negative effects on the environment such as increase in suspended solids in the water column and their consequent transport. An experimental study was conducted to characterize water masses, dynamics, and sedimentation rates on the Ligurian continental shelf (Italy), where both a sand deposit, that could be used for beach nourishment, and a nearby Posidonia oceanica meadow coexist. The environmental plan provides a mathematical simulation of the sediment-dispersion to evaluate the possible impact on the meadow. It has been calculated that the dredging could double the concentration of suspended particles, but its scheduling will preclude a sediment accumulation. All the information obtained from this work will be used to study the environmental feasibility of the sand deposit exploitation and as starting point for drawing up the monitoring plan in case of dredging.

The evolution of density currents and nepheloid bottom layers in the Ross Sea (Antarctica)

In this study we have analyzed the thermohaline, light transmission and particulate matter data, obtained in the western sector of the Ross Sea during the X Italian Expedition, for the purpose of investigating the evolution of the High Salinity Shelf Water in this area. In particular CTD data were used to estimate the baroclinic velocity field. Light transmission and total particulate matter data (from Niskin bottles mounted on a Carousel water sampler) were used to analyze the nepheloid layers and the evolution of the suspended sediments. This basin is characterized by a northward flow of very dense High Salinity Shelf Water ( 1.95°C, S 34.90), much colder than the incoming Circumpolar Deep Water ( 1.20°C, S 34.70). We obtained a scenario in which the High Salinity Shelf Water interacts with the Circumpolar Deep Water along the Antarctic Slope Front, and deviates from its geostrophic equilibrium. Interestingly, this cold dense water mixes with Circumpolar Deep Water at the shelf break and flows downward until it seems to disappear. Below this cold flow, a thin turbulent current has been observed, again moving northward with a high velocity 0.2–1.0 m s . This thin flow also contains high concentration of suspended matter produced by the interaction of the dense water and the bottom sediments. The various elementary mechanisms ruling the dynamics of such down-flows, namely the effects of topographic irregularities, bottom friction, Ekman benthic boundary layers or the effect of the variability of the Antarctic Circumpolar Current, which can push offshore the dense water, are discussed in this paper.

Actual Sedimentation on the Antarctic Continental Shelf (Southern Part of the Ross Sea)

During the austral summer 1994-95 the C.L.I.M.A. Project carried out an oceanographic cruise aimed at improving the caracterization of water masses inside the Ross Sea. A series of 154 CTD casts was performed and water samples were collected to study particulate matter, concentration data and dimensional analyses of particulate matter were correlated with physical characteristics. In the area of the Ross Ice Shelf high concentrations of particulate matter seem to coincide with the caracteristics of “Deep Ice Shelf Waters” and “Warm Core Waters”. The relationship between water masses and characteristics of particulate matter have enabled us to use this one as a natural tracer to identify flow pathways; results have also allowed to define a general hypothesis on actual sedimentation during the austral summer in the proximity of the RIS and at the edge of the continental shelf.

Evaluation of the boundary condition influence on PAH concentrations in the water column during the sediment dredging of a port

The mobilisation of sediments and related contaminants connected to dredging activities is one of the most critical issues to the environmental risk and exposure assessment of a dredging project. The aim of this paper was an investigation of the mobilisation of polycyclic aromatic hydrocarbons (PAHs) due to the dredging of the Port of Genoa (Italy) to identify the temporal and spatial extent of the contaminant transport, and the influence of the dredging and the boundary conditions on it. The results showed relatively low background PAH concentrations in the water column and confirmed the dredging as the primary rising factor of concentrations in the water column, but also showed a complex scenario in which the different environmental and dredging factors forced the concentrations at different levels and moments. The post dredging phase showed PAH values close to the background conditions and the concentrations remained relatively high only for a few PAHs.

The composition and distribution of the particulate matter in the Strait of Magellan (Chile) during the 1991 and 1995 Italian campaigns

During 1991 and 1995, the Italian National Program for Antarctic Research carried out two oceanographic campaigns in the framework of the International (Strait of) Magellan Project. In this paper, we describe the distribution, biochemical composition, and mineralogical characteristics of particulate matter and the characteristics of the water masses defining microbasins in the Strait of Magellan. The data analyses highlighted differences in quality and quantity of the suspended matter and its organic component in the basins that make up the Strait and the Pacific Ocean. The westernmost basin is subject to an eastward flow from the Pacific Ocean, and continental runoff in the surface layers, which are consequently rich in organic matter with a high C:N ratio. The central basin, Isla Carlos III–Segunda Angostura, is characterized by the mixing of Sub-Antarctic Pacific waters, continental runoff, and glacio-fluvial waters: The basin has the lowest particulate matter concentration, but at Paso Ancho showed high concentrations of organic matter with a lower C:N ratio. The easternmost basin, Segunda Angostura-Atlantic entrance, is characterized by the mixing of the water column due to strong Atlantic tides and showed high concentration of particulate matter with a high detritic component. Generally, the organic matter concentrations showed significant differences during the cruises, being higher in 1991. Using the multivariate discriminant factor analysis to determine whether statistically significant differences existed between defined sampling areas, we determined that temperature, particulate organic carbon, and total particulate matter were the variables most important for the difference between areas.